2015 Shatters Hottest Year Mark; 2016 Hot on its Heels?

It’s official: 2015 was the hottest year on record, beating out 2014
by the widest margin in 136 years of record keeping, U.S. government
agencies announced Wednesday.

The year’s incredible heat serves as a stark reminder of how much the
Earth’s temperature has risen due to the steady buildup of
heat-trapping greenhouse gases in the atmosphere from human activities
like power generation, transportation and clear cutting of forests. That
temperature reached the point in 2015 where it was 1°C (1.8°F)
above that of the late 19th century at the same time as carbon dioxide
levels likely permanently rose above 400 parts per million.

“2015 was remarkable even in the context of the larger, long-term
warming trend,” Gavin Schmidt, director of NASA’s Goddard Institute for
Space Studies, said in a statement.

Both NASA and the National Oceanic and Atmospheric Administration (NOAA) reported that 2015 easily took over the top spot from 2014. By NASA’s measure, 2015 was 0.23°F (0.13°C) warmer than 2014 — the second largest-ever jump from a previous record. By NOAA’s measure it
was 1.62°F (0.9°C) above the 20th century average and the largest jump
from a previous record, at 0.29°F (0.16°C) above 2014.

“That’s the rather remarkable part of the story, we think, this
year,” Thomas Karl, director of NOAA's National Centers for
Environmental Information, said during a press teleconference.

The two agencies use slightly different methods of assembling the
global temperature data, leading to the slightly varying numbers, though
both datasets show the clear warming of the planet.

The oceans were one of the clear hot spots on the globe during the
year, particularly the Indian Ocean and the tropical Pacific Ocean,
which was under the influence of an incredibly strong El Niño. Record
warmth was found in parts of Europe, Africa, Asia, Australia, South
Africa and North America. It was the second hottest year on record for the U.S., helped by an incredibly toasty December in the eastern half of the country.

“We would not have seen the record warming without the long-term trend,” Schmidt said.

The top 10 hottest years on record. Click to enlarge.

The end of the year also saw international negotiators in Paris agree to a plan
to limit greenhouse gas emissions to keep that temperature from rising
beyond 2°C (3.6°F) above pre-industrial levels to limit the adverse
impacts of warming, such as melting glaciers, rising sea levels and
potentially more extreme weather.

But this new record may not stand for long, as one of the strongest
El Niños ever measured combines with the continued warming of the planet
to potentially push 2016 to yet another record.

This could be the case even if the tropical Pacific transitions into a
La Niña later this year, Barnston said. La Niña is the cold counterpart
to El Niño, featuring below-normal temperatures in the tropical Pacific
Ocean and cooler global temperatures.

The overall background warming of the globe means that even La Niña
years now are warmer than El Niño years of previous decades. And the
temperature effects of a La Niña later this year wouldn’t be felt until
the year was nearly over, Barnston said.

Temperature rankings for each continent for 2015. ​Click to enlarge.

The U.K.’s Met Office predicts that 2016 will be 1.5°F (0.84°C) above
the 1961-1990 average, while 2015 was 1.3°F (0.72°C) above this
average. (That prediction assumes there are no major volcanic eruptions,
which have a cooling influence.)

"This forecast suggests that by the end of 2016 we will have seen
three record, or near-record years in a row for global temperatures,” Adam Scaife, head of long-range prediction at the Met Office, said in a statement.

Scientists don’t expect every year to be warmer than the last, as
natural fluctuations like La Niña can have a cooling influence, but
overall manmade warming tips the odds in favor of record hot over record
cold. The last globally record cold year was 1911, while 15 of the 16
hottest years on record have occurred since 2001, according to NASA.